Constant velocity universal joint

ABSTRACT

The tripod member has three trunnions which are projected radially. Each of the trunnions carries a roller, and this roller is accommodated in one of the track grooves in the outer joint member. The outer peripheries of the rollers and the roller guideways make angular contact with each other. Support rings are fitted onto the outer peripheries of the trunnions. These support rings and the rollers are assembled (unitized) via a plurality of needle rollers to constitute roller assemblies capable of relative rotations. In longitudinal sections, the outer peripheries of the trunnions have straight shapes parallel to the axes of the trunnions. In cross sections, the outer peripheries are elliptic in shape, with their respective major axes perpendicular to the axis of the joint. The inner peripheries of the support rings have arcuate convex sections.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a constant velocity universaljoint for use in power transmission devices in motor vehicles andvarious industrial machines. In particular, the invention relates to atripod type constant velocity universal joint.

[0002] Tripod type constant velocity universal joints are used, forexample, as an element in a power transmission device for transmittingrotational power from a car engine to wheels (as a joint for couplingdrive shafts or propeller shafts).

[0003] In general, a tripod type constant velocity universal joint ischiefly composed of an outer joint member and a tripod member. The outerjoint member has an inner periphery provided with three track grooves,each of which has axial roller guideways on both sides. The tripodmember has three radially-projecting trunnions. A roller is rotatablyarranged on each of the trunnions. The trunnions of the tripod memberand the roller guideways in the outer joint member engage with eachother in the direction of rotation via the rollers so that rotationaltorque is transmitted from a drive side to a driven side at constantvelocity. The individual rollers rotate about the trunnions and roll onthe roller guideways as well, absorbing relative axial displacements andangular displacements between the outer joint member and the tripodmember. In the meantime, also absorbed are axial displacements of theindividual trunnions to the roller guideways, the axial displacementsresulting from phase changes in the direction of rotation when the outerjoint member and the tripod member transmit rotational torque with someoperating angle therebetween.

[0004] Among factors contributing to the vibration characteristics of aconstant velocity universal joint of this type are induced thrust andslide resistance. The induced thrust is a periodic varying forceproduced by friction between internal parts of the constant velocityuniversal joint when the joint transmits rotational torque with anoperating angle. That is, due to the rotational motion, the individualtrunnions of the tripod member and the rollers inevitably repeatrelative axial reciprocation to the roller guideways. In that case,friction occurs at such portions as between the rollers and the rollerguideways, and between the rollers and the trunnions. This frictionproduces the induced thrust. Thus, the induced thrust is a varying forceinherent in a constant velocity universal joint, inevitably occurring inrelation to the internal structure and rotational motion of the joint.In the case of a tripod type constant velocity universal joint, theinduced thrust consists chiefly of a variation component of third order(tertiary rotational component) because the numbers of trunnions androllers are three. Meanwhile, the slide resistance is a periodic varyingforce produced by friction between the internal parts when externalvibrations are input to the constant velocity universal joint undertorque. In other words, the slide resistance indicates the vibrationtransfer characteristics of the constant velocity universal joint.

[0005] For the power transmission device of a motor vehicle, thevibrations resulting from the induced thrust and slide resistance of theconstant velocity universal joint are rather small in level as comparedwith engine vibrations and the like, and thus matter little bythemselves. Nevertheless, the vibrations, if approaching the enginevibrations and the like in frequency, cause resonance phenomena. Theinduced thrust causes the rolling of a car body at starts and underacceleration, as well as muffled noise, beat noise, and so on. The slideresistance causes an increase of idling vibrations and the like (inparticular, affecting the D-range idling vibrations). Accordingly, theinduced thrust and slide resistance in the constant velocity universaljoint have significant influence on the NVH (noise vibration harshness)performances of the motor vehicle. In particular, the induced thrust isever increasing in the degree of influence on the NVH performances, withwidening regular-use angles (vehicle-mounted angles) of the joint andincreasing torque in recent times. Then, in terms of vehicle design, itmeans that the values of the induced thrust and slide resistance ofconstant velocity universal joints constitute greater constraints on thelayout design of power transmission systems.

SUMMARY OF THE INVENTION

[0006] An object of the present invention is to regulate the inducedthrust and slide resistance of a constant velocity universal joint,thereby easing the constraints on the layout design of a powertransmission system and providing a constant velocity universal joint oflow vibration and high reliability in quality.

[0007] Another object of the present invention is to further reduce andstabilize the induced thrust and slide resistance of a constant velocityuniversal joint, and then provide a constant velocity universal jointthat is excellent in durability, productivity, and strength, low invibration, and compact in size.

[0008] To achieve the foregoing objects, the present invention providesa constant velocity universal joint including: an outer joint memberhaving three track grooves formed in its inner periphery, each of thetrack grooves having axial roller guideways on both sides; a tripodmember having three radially-projecting trunnions; and rollersrespectively arranged on the trunnions of the tripod member, the rollersbeing guided by the roller guideways. Here, at least either inducedthrust or slide resistance is regulated within a specification. Thisincreases the reliability as to the induced thrust and/or slideresistance of the constant velocity universal joint, thereby easing theconstraints on the layout design of the power transmission system andimproving the design flexibility. The constant velocity universal jointalso improves in vehicle mountability. Moreover, the reliability as tothe vibration characteristics of the constant velocity universal jointincreases to contribute to stabilized NVH performances of a vehicle.

[0009] Specifically, the number of revolutions R=100-500 (rpm) and anoperating angle θ=0-14 (deg) are employed as common conditions. Then,under load torque T=0.1×Ts (N·m) {condition (X1)}, the tertiaryrotational component of the induced thrust may be regulated to or below30 N (RMS: Root Mean Square), or preferably to or below 20 N (RMS).Under load torque T=0.2×Ts (N·m) {condition (X2)}, the tertiaryrotational component of the induced thrust may be regulated to or below55 N (RMS), or preferably to or below 35 N (RMS). Under load torqueT=0.3×Ts (N·m) {condition (X3)}, the tertiary rotational component ofthe induced thrust may be regulated to or below 80 N (RMS), orpreferably to or below 55 N (RMS). These regulations allow the provisionof a constant velocity universal joint of low vibration and high qualityreliability, aside from the effects described above. They alsocontribute to improved NVH performances of a motor vehicle.

[0010] Furthermore, with the number of revolutions R=0 (rpm), anoperating angle θ=0-10 (deg), load torque T=98-196 (N·m), and avibrating frequency f=15-40 (Hz) as common conditions, the slideresistance may be regulated to or below 40 N (peak to peak) undervibrating amplitude=±0.01 to ±0.03 (mm) {condition (Y1)}. Undervibrating amplitude=±0.05 to ±0.08 (mm) {condition (Y2)}, the slideresistance may be regulated to or below 60 N (peak to peak). Undervibrating amplitude=±0.10 to ±0.25 (mm) {condition (Y3)}, the slideresistance may be regulated to or below 80 N (peak to peak). Here, the“peak to peak” means the total of the absolute values of positive andnegative peak values. These regulations allow the provision of aconstant velocity universal joint of low vibration and high qualityreliability, aside from the effects described above. They alsocontribute to improved NVH-performances of a motor vehicle.

[0011] In the configurations described above, it is preferable toprovide roller assemblies for allowing tilting movements of the rollerswith respect to the trunnions. These roller assemblies may include therollers and support rings for supporting the rollers rotatably, thesupport rings being fitted onto the outer peripheries of the trunnions.Here, the inner peripheries of the support rings have an arcuate convexsection. The outer peripheries of the trunnions are straight in alongitudinal section, and so shaped in a cross section as to makecontact with the inner peripheries of the support rings in directionsperpendicular to the axis of the joint and create clearances with theinner peripheries of the support rings in the axial direction of thejoint. In this configuration, the roller assemblies that include therollers and the support rings make unitary tilting movements withrespect to the trunnions. Here, the term “tilting movements” refers tothe tilts the axes of the support rings and rollers make with respect tothe axes of the trunnions, within the planes containing the axes of thetrunnions.

[0012] The cross-sectional shape of such a trunnion as makes contactwith the inner periphery of a support ring in a direction perpendicularto the axis of the joint and creates a clearance with the innerperiphery of the support ring in an axial direction of the jointtranslates into that the faces opposed to each other in the axialdirection of the tripod member retreat toward each other, i.e., tosmaller diameters than the diameter of an imaginary cylindrical surface.Among concrete examples thereof is a generally elliptic shape. The term“generally elliptic shape” includes not only literal ellipses, but alsoother shapes generally referred to as ovals and the like.

[0013] Due to the change of their cross sections from the conventionalcircular shape to the shape described above, the trunnions can tilt withrespect to the outer joint member without changing the orientation ofthe roller assemblies when the joint operates with an operating angle.Besides, the contacting ellipses of the support rings with the outerperipheries of the trunnions approach from oblongs to points in shape.This reduces friction moments that act to tilt the roller assemblies. Asa result, the roller assemblies are stabilized in orientation, wherebythe rollers are retained parallel to the roller guideways for smoothrolling. This means reductions of the induced thrust and slideresistance, accompanied with a narrowed range of variations of thesevalues. Accordingly, in the constant velocity universal joint of thisconfiguration, the specifications of the induced thrust and slideresistance can be made smaller as described above. Besides, these valuescan be accurately regulated within the specifications. This results in alow-vibration constant velocity universal joint of higher reliability.

[0014] The roller assemblies are interposed between the trunnions andthe outer joint member for the sake of torque transmission. In constantvelocity universal joints of this kind, the transmission direction oftorque is always perpendicular to the axis of the joint. Therefore, aslong as they make contact in the transmission direction of torque, thetrunnions and the support rings can perform torque transmission withouttrouble even when they have clearances therebetween in the axialdirections of the joint.

[0015] In the configurations described above, the generator to the innerperipheries of the support rings may consist of a combination of an arcportion at the center and relief portions on both sides. The arc portionpreferably has such a radius of curvature as allows 2-3° tilts of thetrunnions. In addition, a plurality of rolling elements may beinterposed between the support rings and the rollers so as to make thesupport rings and the rollers capable of relative rotations. The rollingelements may be needle rollers. Furthermore, the outer peripheries ofthe rollers may be formed into a spherical shape (perfect sphericalsurfaces or torus surfaces) so that the spherical outer peripheries ofthe rollers and the roller guideways in the outer joint member makeangular contact with each other. The angular contact between the rollersand the roller guideways makes the rollers less prone to vibrate,thereby stabilizing the orientation of the rollers. As a result, therollers can roll on the roller guideways with smaller resistance whenmoving along the axial direction of the outer joint member. The specificconfigurations to establish such angular contact include tapered orGothic arch cross sections of the roller guideways.

[0016] The roller assemblies may include the rollers and support ringsfor supporting the rollers rotatably, the support rings being fittedonto the outer peripheries of the trunnions, wherein the outerperipheries of the trunnions have a convex spherical shape and the innerperipheries of the support rings have a cylindrical or conical shape. Inthis configuration, the roller assemblies including the rollers and thesupport rings make unitary tilting movements with respect to thetrunnions.

[0017] According to this invention, the following effects are obtained.

[0018] (1) At least either the induced thrust or the slide resistance isregulated within the specifications, and the reliability as to thesecharacteristics is high. This eases the constraints on the layout designof the power transmission system and improves the design flexibility.Besides, the constant velocity universal joint also improves in vehiclemountability. Moreover, there liability as to the vibrationcharacteristics of the constant velocity universal joint increases tocontribute to stabilized NVH performances of a vehicle.

[0019] (2) The tertiary rotational component of the induced thrust isregulated to or below 30 N (RMS) under the condition (X1), to or below55 N (RMS) under the condition (X2), or to or below 80 N (RMS) under thecondition (X3). In addition to the effect (1) described above, theseregulations achieve a reduction and stabilization of the induced thrust,thereby making it possible to provide a constant velocity universaljoint having excellent low-vibration characteristics and highreliability. This contributes to improved NVH performances of a motorvehicle. Moreover, the constant velocity universal joint becomes capableof regular use at wider angles, which has been difficult, with a furtherimprovement in its vehicle mountability.

[0020] (3) Furthermore, the slide resistance is regulated to or below 40N (peak to peak) under the condition (Y1), to or below 60 N (peak topeak) under the condition (Y2), or to or below 80 N (peak to peak) underthe condition (Y3). In addition to the effects (1) and (2) describedabove, these regulations achieve a reduction and stabilization of theslide resistance, thereby making it possible to provide a constantvelocity universal joint having excellent low-vibration characteristicsand high reliability. This contributes to improved NVH performances of amotor vehicle.

[0021] To achieve the foregoing objects, the present invention alsoprovides a constant velocity universal joint including: an outer jointmember having three track grooves each having circumferentially-opposedroller guideways; a tripod member having three radially-projectingtrunnions; rollers inserted into the track grooves; and rings fittedonto the trunnions, for supporting the rollers rotatably; the rollersbeing capable of moving along the roller guideways in the axialdirection of the outer joint member. Here, letting T_(PCD) stand for thepitch circle diameter of the track grooves and S_(PCD) for the pitchcircle diameter of a spline hole formed in the tripod member, the ratioT_(PCD)/S_(PCD) is set within the range of 1.7-2.1. The ratio of thediameter D_(J) of the trunnions to the pitch circle diameter S_(PCD) ofthe spline hole, or D_(J)/S_(PCD), is set within the range of 0.6-1.0.The ratio of the diameter D_(R) of the rollers to the pitch circlediameter S_(PCD) of the spline hole, or D_(R)/S_(PCD), is set within therange of 1.4-2.3.

[0022] In a tripod type constant velocity universal joint for use in amotor vehicle's power transmission system, the pitch circle diameterS_(PCD) of the spline hole in the tripod member is determined by thestrength required of the joint. Meanwhile, the outer diameter D_(O) ofthe outer joint member is limited since the joint must be mounted on apredetermined space in a vehicle. Thus, the individual parts of theconstant velocity universal joint need to be put into appropriatedimensional proportions to one another. The ratio T_(PCD)/S_(PCD)defines the pitch circle diameter T_(PCD) of the track grooves. Morespecifically, if the track grooves are made so small in pitch circlediameter TPCD that the ratio T_(PCD)/S_(PCD) falls below 1.7, therearises a problem of interference between the rollers and the shouldersof the trunnions. Besides, the surface pressures at the contactportions, such as between the trunnions and the rings, increase to causea drop in durability. On the other hand, if the track grooves are madeso large in pitch circle diameter T_(PCD) that the ratio T_(PCD)/S_(PCD)exceeds 2.10, the outer joint member increases in outer diameter D_(O)with deterioration in vehicle mountability. Additionally, given that theouter diameter of the outer joint member is fixed, there remains littlespace for the roller assemblies.

[0023] The ratio D_(J)/S_(PCD) defines the diameter DJ of the trunnions.More specifically, if the trunnions are made so small in major diameterD_(J) that the ratio D_(J)/S_(PCD) falls below 0.6, the constantvelocity universal joint cannot function satisfactory. On the otherhand, if the trunnions are made so large in major diameter that theratio D_(J)/S_(PCD) exceeds 1.0, there remains little space for theroller assemblies to be arranged in, which is dissatisfactory in termsof the limit in the outer diameter.

[0024] The ratio D_(R)/S_(PCD) defines the diameter DR of the rollers.More specifically, if the rollers are made so small in outer diameterD_(R) that the ratio D_(R)/S_(PCD) falls below 1.4, the surfacepressures between the rollers and the roller guideways increase to dropthe durability. Besides, the reduction in the thickness of the rollerscauses a problem of deteriorated strength. Meanwhile, when the rollersare made so large in outer diameter D_(R) that the ratio D_(R)/S_(PCD)exceeds 2.3, the outer joint member becomes thinner to drop inforgeability if the diameter D_(O) of the outer joint member is given.This also produces a problem of shaft interference, as well as advancesinterference of the outer joint member with cup bottoms, yielding anincreased cup depth and a greater weight.

[0025] In the configuration described above, the rings may be shapedinto a spherical cross section while the trunnions are so shaped in across section as to make contact with the inner peripheries of the ringsin directions perpendicular to the axis of the joint and createclearances with the inner peripheries of the rings in the axialdirection of the joint. Besides, the ratio T_(PCD)/S_(PCD) is set withinthe range of 1.72-2.10. The ratio of the dimension D_(JL) of thetrunnions in the directions perpendicular to the axis of the joint tothe pitch circle diameter S_(PCD) of the spline hole, or D_(JL)/S_(PCD),is set within the range of 0.63-0.94. The ratio D_(R)/S_(PCD) is setwithin the range of 1.47-2.21.

[0026] Here, the cross-sectional shape of such a trunnion as makescontact with the inner periphery of a ring in a direction perpendicularto the axis of the joint and creates a clearance with the innerperiphery of the ring in an axial direction of the joint translates intothat the faces opposed to each other in the axial direction of thetripod member retreat toward each other, i.e., to smaller diameters thanthe diameter of an imaginary cylindrical surface. Among concreteexamples thereof is an ellipse. The term “ellipse” includes not onlyliteral ellipses, but also other shapes generally referred to as ovalsand the like.

[0027] Due to the change of their cross sections from the conventionalcircular shape to the shape described above, the trunnions can tilt withrespect to the outer joint member without changing the orientation ofthe roller assemblies when the joint operates with an operating angle.Besides, the contacting ellipses of the rings with the outer peripheriesof the trunnions approach from oblongs to points in shape. This reducesfriction moments that act to tilt the roller assemblies. As a result,the roller assemblies are stabilized in orientation, whereby the rollersare retained parallel to the roller guideways for smooth rolling. Thiscontributes to a reduction of the slide resistance, and by extension tothe reduction of the induced thrust. There is an additional advantage inthat the trunnions improve in flexural strength due to increased sectionmoduli at the bottom portions of the trunnions.

[0028] More specifically, the adoption of the cross-sectional shapes ofthe trunnions as described above eases the contact pressures against therings and avoids a drop in the strength of the trunnions. Besides, thetrunnions can tilt without inclining the rings. This prevents therollers from inclination and allows the rollers to roll smoothly on theroller guideways. As a result, it becomes possible to omit collars whichare sometimes arranged on the track grooves of the outer joint memberwith an aim to restrain the inclination of the rollers. The omission ofthe collars not only reduces the outer joint member in weight andsimplifies the machining thereto, but also eliminates the slide contactsbetween the rollers and the collars. This consequently achieves afurther decrease of the slide resistance and a reduction of the inducedthrust.

[0029] The roller assemblies are interposed between the trunnions andthe outer joint member for the sake of torque transmission. In constantvelocity universal joints of this kind, the transmission direction oftorque is always perpendicular to the axis of the joint. Therefore, aslong as they make contact in the transmission direction of torque, thetrunnions and the support rings can perform torque transmission withouttrouble even when they have clearances therebetween in the axialdirections of the joint.

[0030] The numerical ranges of the ratio T_(PCD)/S_(PCD), the ratioD_(JL)/S_(PCD), and the ratio D_(R)/S_(PCD) are determined on the basesfundamentally identical to those described above.

[0031] Moreover, in the configuration described above, the ratio of theouter diameter D_(O) of the outer joint member to the pitch circlediameter S_(PCD) of the spline hole, or D_(O)/S_(PCD), may be set withinthe range of 2.78-3.77. The ratio D_(O)/S_(PCD) defines the diameterD_(O) of the outer joint member. More specifically, if the outer jointmember is made so small in outer diameter Do that the ratio DO/SPCDfalls below 2.78, the surface pressures at the individual contactportions increase to lower the durability. In addition, the stresses onthe individual parts increase to cause deterioration in strength. On theother hand, increasing the outer diameter D_(O) of the outer jointmember to such an extent that the ratio D_(O)/S_(PCD) exceeds 3.77 notonly deteriorates the vehicle mountability but also yields a weightincrease.

[0032] Moreover, in the configuration described above, the ratio of thebarrel width H_(T) of the tripod member to the pitch circle diameterS_(PCD) of the spline hole, or H_(T)/S_(PCD), may be set within therange of 0.81-1.22. The ratio H_(T)/S_(PCD) defines the width H_(T) ofthe tripod member. If the tripod member is made so small in width H_(T)that the ratio H_(T)/S_(PCD) falls below 0.81, the length of the splinefit decreases to lower the spline strength. On the other hand, if thetripod member is made so large in width HT that the ratio H_(T)/S_(PCD)exceeds 1.22, there arises a problem of interference between the rollersand the shoulders of the trunnions.

[0033] Moreover, in the configuration described above, the ratio of thewidth H_(R) of the rollers to the pitch circle diameter S_(PCD) of thespline hole, or H_(R)/S_(PCD), may be set within the range of 0.38-0.67.The ratio H_(R)/S_(PCD) defines the width H_(R) of the rollers. Morespecifically, if the rollers are made so small in width that the ratioH_(R)/S_(PCD) falls below 0.38, the surface pressures between therollers and the roller guideways increase to drop the durability.Besides, the reduction in the rigidity of the rollers results ininsufficient strength. Meanwhile, when the rollers are made so large inwidth H_(R) that the ratio H_(R)/S_(PCD) exceeds 0.67, the rollers comeinto interference with the shoulders of the trunnions. Moreover, if theouter diameter of the outer joint member is given, the outer jointmember becomes thinner to drop in forgeability.

[0034] Moreover, in the configuration described above, the ratio of theradius of curvature R_(R) of the rollers' outer peripheries to the pitchcircle diameter S_(PCD) of the spline hole, or R_(R)/S_(PCD), may be setwithin the range of 0.19-1.11. The ratio R_(R)/S_(PCD) defines theradius of curvature R_(R) of the rollers' outer peripheries. Morespecifically, if the outer peripheries of the rollers are made so smallin the radius of curvature that the ratio R_(R)/S_(PCD) falls below0.19, the rollers yield drop in rigidity into insufficient strength.Meanwhile, when the outer peripheries of the rollers are made so largein the radius of curvature that the ratio R_(R)/S_(PCD) exceeds 1.11,the outer joint member becomes thinner to drop in forgeability if thediameter Do of the outer joint member is given.

[0035] According to this invention, the following effects are obtained.

[0036] (1) The dimensions of the individual parts of the constantvelocity universal joint are brought into appropriate proportions to oneanother. Besides, configurations for a constant velocity universal jointwith excellent low-vibration characteristics are provided.

[0037] (2) In particular, the rings are shaped into a spherical crosssection while the trunnions are so shaped in a cross section as to makecontact with the inner peripheries of the rings in directionsperpendicular to the axis of the joint and create clearances with theinner peripheries of the rings in the axial direction of the joint. Thisallows the trunnions to tilt with respect to the outer joint memberwithout changing the orientation of the roller assemblies when the jointoperates with an operating angle. Besides, the contacting ellipses ofthe rings with the outer peripheries of the trunnions approach fromoblongs to points in shape, which reduces friction moments that act totilt the roller assemblies. In addition, the contacts between thetrunnions and the inner peripheries of the rings always stay at thewidth centers of the rings. Therefore, even when rolling elements suchas needle rollers are interposed between the rings and the rollers,these rolling elements make stable rolling. As a result, the rollerassemblies are stabilized in orientation, whereby the rollers areretained parallel to the roller guideways for smooth rolling. Thiscontributes to a reduction of the slide resistance, and by extension tothe reduction of the induced thrust. There is an additional advantage inthat the trunnions improve in flexural strength due to increased sectionmoduli at the bottom portions of the trunnions.

[0038] (3) The constant velocity universal joints of the presentinvention, when applied to a motor vehicle's drive shaft in particular,can contribute to improvements in automotive NVH performances associatedwith the slide resistance and induced thrust, thereby increasing designflexibility of portions around the axles of the vehicle.

[0039] Now, with an eye to yet an effective reduction and thestabilization of the induced thrust and slide resistance, the followingconsiderations can be made.

[0040] From among the constant velocity universal joints of the presentinvention having been described, take, for example, the one in which:the inner peripheries of the support rings have an arcuate convexsection; and the outer peripheries of the trunnions are straight in alongitudinal section, and so shaped in a cross section as to makecontact with the inner peripheries of the support rings in directionsperpendicular to the axis of the joint and create clearances with theinner peripheries of the support rings in the axial direction of thejoint. As exaggeratedly shown in FIG. 26, slight radial clearances existbetween the parts constituting each roller assembly A (between theroller 34 and the needle rollers 36, between the support ring 32 and theneedle rollers 36), between the roller 34 and the roller guideway 14,and between the support ring 32 and the trunnion 22 when the joint isput under no load. Therefore, as exaggeratedly shown in FIG. 27, when aload is applied to among the trunnion 22, the roller assembly A, and theroller guideway 14 to reduce the clearances mentioned above inrotational torque transmission, the axis X of the trunnion 22 tilts withrespect to the axis Y of the roller assembly A by the amountcorresponding to the clearances mentioned above (tilt angle β) withinthe plane of the diagram (within a section perpendicular to the axis ofthe joint). This tilt of the trunnion 22 deviates the direction of theload F applied to the contact portion S between the trunnion 22 and theroller assembly A (the contact point between the outer periphery 22 a ofthe trunnion 22 and the inner periphery 32 c of the support ring 32)from the direction of torque transmission (the direction of the tangentat the contact point S to a circle about the joint center O) to aninward direction. This produces a component of force f directed to thetrunnion bottom (hereinafter, this component of force will be referredto as “inward component f”). Moreover, the support ring 32 and the lockrings 33, 35 also have slight axial clearances therebetween, so that thesupport ring 32 can make an axial relative shift with respect to theroller 34 by the amount corresponding to the axial clearances. Thus,when the above-described inward component f is applied, the support ring32 makes a relative shift toward the trunnion bottom and comes intocontact with the lock ring 35. Accordingly, the center line L1 passingthrough the center of curvature of the inner periphery 32 s of thesupport ring 32 makes a Δh shift toward the trunnion bottom from thecenter line L2 passing through the center of curvature of the outerperiphery 34 a of the roller 34. This consequently promotes the inwardcomponent f in magnitude. Then, due to such an inward component f, theroller assembly A makes a clockwise tilt within the plane of thediagram, with respect to the roller guideway 14. This increases thechances for the outer periphery 34 a of the roller 34 to contact withthe trunnion-bottom side of the roller guideway 14 in the non-loaddirection (not shown). Therefore, the smooth rolling of the roller 34 issometimes hampered to affect the induced thrust and slide resistance ofthe joint.

[0041] In view of the foregoing considerations, the present inventionprovides a constant velocity universal joint including: an outer jointmember having three axial track grooves formed in its inner periphery,each of the track grooves having axial roller guideways on both sides; atripod member having three radially-projecting trunnions; and rollerassemblies respectively mounted on the trunnions of the tripod member;the roller assemblies including rollers to be guided along the rollerguideways in directions parallel to the axis of the outer joint memberand support rings for supporting the rollers rotatably, the rollerassemblies being capable of tilting movements with respect to thetrunnions. Here, the constant velocity universal joint further includestilt suppressing means for suppressing tilts of the roller assemblieswithin a cross section perpendicular to the axis of the joint due toinward components of load applied to contact portions between thetrunnions and the roller assemblies. Here, the term “inward components”refers to components of loads toward the trunnion bottoms, resultingfrom an inward deviation of the loads applied to the contact portionsbetween the trunnions and the roller assemblies from the direction oftorque transmission.

[0042] For the tilt suppression means mentioned above, a configurationmay be adopted in which two-point angular contact is established betweenthe outer peripheries of the rollers and the roller guideways, and thecontact angle at angular contact points on the trunnion-bottom sides ismade greater than the contact angle at angular contact points on thetrunnion-extremity sides. According to this configuration, the angularcontact between the rollers and the roller guideways stabilizes theorientation of the rollers with respect to the roller guideways. Inaddition, since the contact angle at the angular contact points on thetrunnion-bottom sides is made greater than the contact angle at theangular contact points on the trunnion-extremity sides, the inwardcomponents can be exerted higher at the angular contact points on thetrunnion-bottom sides. Accordingly, the tilts of the roller assemblywithin a section perpendicular to the axis of the joint are suppressedto ensure smooth rolling of the rollers. Incidentally, the rollerguideways may be shaped to Gothic arch, tapered (V-shaped), or paraboliccross sections so as to achieve the angular contact.

[0043] Moreover, the tilt suppressing means may adopt a configuration inwhich the outer peripheries of the rollers are shaped into arcuateconvex sections having the centers of curvature in the vicinities oflines parallel to the axes of the rollers, the lines passing through thecontact portions. According to this configuration, the above-mentionedcontact portions, or the points of application of the inward components,and the centers of curvature of the outer peripheries of the rollers, orthe fulcrums of the tilts of the roller assemblies, are brought near toor coincident with each other in the radial directions of the rollerassemblies. This reduces the tilting moments acting on the rollerassemblies. Therefore, the tilts of the roller assemblies within asection perpendicular to the axis of the joint are suppressed to ensurethe smooth rolling of the rollers.

[0044] The above-described constant velocity universal joint may employsuch a configuration as includes the rollers to be guided by rollerguideway and support rings for supporting the rollers rotatably,wherein: the inner peripheries of the support rings have an arcuateconvex section; and the outer peripheries of the trunnions are straightin a longitudinal section, and so shaped in a cross section as to makecontact with the inner peripheries of the support rings in directionsperpendicular to the axis of the joint and create clearances with theinner peripheries of the support rings in the axial direction of thejoint.

[0045] The cross-sectional shape of such a trunnion as makes contactwith the inner periphery of a support ring in a direction-perpendicularto the axis of the joint and creates a clearance with the innerperiphery of the support ring in an axial direction of the jointtranslates into that the faces opposed to each other in the axialdirection of the tripod member retreat toward each other, i.e., tosmaller diameters than the diameter of an imaginary cylindrical surface.Among concrete examples thereof is a generally elliptic shape. The term“generally elliptic shape” includes not only literal ellipses, but alsoother shapes generally referred to as ovals and the like.

[0046] Due to the change of their cross sections from the conventionalcircular shape to the shape described above, the trunnions can tilt withrespect to the outer joint member without changing the orientation ofthe roller assemblies (roller assemblies) when the joint operates withan operating angle. Besides, the contacting ellipses of the supportrings with the outer peripheries of the trunnions approach from oblongsto points in shape. This reduces friction moments that act to tilt theroller assemblies. As a result, the roller assemblies are stabilized inorientation, whereby the rollers are retained parallel to the rollerguideways for smooth rolling. This contributes to a reduction of theslide resistance, and by extension to the reduction of the inducedthrust.

[0047] In the configuration described above, the generator to the innerperipheries of the support rings may consist of a combination of an arcportion at the center and relief portions on both sides. The arc portionpreferably has such a radius of curvature as allows 2-3° tilts of thetrunnions.

[0048] In the constant velocity universal joint of the above-describedconfiguration, axial relative movements of the rollers and the supportrings can be retained from both sides by lock means such as lock ringsand lock collars, so as to ensure the unity of the roller assemblies asassemblies. Nevertheless, axial clearances must be secured between therollers/support rings and the lock means. Then, the support rings arestill capable of axial relative movements to the rollers by the amountscorresponding to the axial clearances. Therefore, when theabove-described inward components are applied, the support rings makerelative movements toward the trunnion bottoms, with respect to therollers. Accordingly, the center lines passing through the centers ofcurvature of the inner peripheries of the support rings make a shifttoward the trunnion bottoms, from the center lines passing through thecenters of curvature of the outer peripheries of the rollers. As aresult, the inward components are promoted in magnitude. To preventthis, the above-described tilt suppressing means may adopt such aconfiguration as establishes coincidence between the center linespassing through the respective centers of curvature of the outerperipheries of the rollers and the center lines passing through therespective centers of curvature of the inner peripheries of the supportrings when the support rings make relative movements to the trunnionbottoms with respect to the rollers due to clearances between parts thatconstitute the roller assemblies. This configuration reduces theabove-described inward components. As a result, the tilts of the rollerassemblies within a section perpendicular to the axis of the joint aresuppressed to ensure the smooth rolling of the rollers.

[0049] Moreover, the above-mentioned tilt suppressing means may includethe outer peripheries of the trunnions, inclined so as to spread outtoward the trunnion bottoms in their longitudinal sections. According tothis configuration, even when the axes of the trunnions tilt withrespect to the axes of the roller assembly within the sectionperpendicular to the axis of the joint, the tilts of the outerperipheries of the trunnions in themselves are suppressed or cancelledout. This reduces the above-described inward components. As a result,the tilts of the roller assemblies within the section perpendicular tothe axis of the joint are suppressed to ensure the smooth rolling of therollers.

[0050] Any of the specific configurations of the tilt suppressing meansdescribed above may be employed by itself. Two or more configurationsmay be used in combination.

[0051] In the configurations described above, a plurality of rollingelements may be interposed between the support rings and the rollers soas to make the support rings and the rollers capable of relativerotations. The rolling elements may be needle rollers, balls, and thelike.

[0052] According to this invention, the tilts of the roller assembliesresulting from the inward components of loads applied to the contactportions between the trunnions and the roller assemblies are suppressedto achieve more effective reduction and stabilization of the inducedthrust and slide resistance in a joint. This makes it possible toprovide a tripod type constant velocity universal joint of yet lowervibration.

[0053] The nature, principle, and utility of the invention will becomemore apparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts aredesignated by like reference numerals or characters.

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In the accompanying drawings:

[0055] FIGS. 1(A)-1(C) show a first embodiment of the present invention,

[0056]FIG. 1(A) being a partially-sectioned end view,

[0057]FIG. 1(B) a sectional view perpendicular to a trunnion in FIG.1(A),

[0058]FIG. 1(C) a sectional view of a support ring for explaining acontacting ellipse;

[0059]FIG. 2(A) is a longitudinal sectional view showing the constantvelocity universal joint of FIGS. 1(A)-1(C) with an operating angle, and

[0060]FIG. 2(B) is a schematic side view of the tripod member in FIG.2(A);

[0061] FIGS. 3(A)-3(C) show a second embodiment of the presentinvention,

[0062]FIG. 3(A) being a partially-sectioned end view,

[0063]FIG. 3(B) a sectional view perpendicular to a trunnion in FIG.3(A),

[0064]FIG. 3(C) a longitudinal sectional view with an operating angle;

[0065]FIG. 4 is an enlarged sectional view of a support ring in FIGS.3(A)-3(C);

[0066] FIGS. 5(A) and 5(B) show a third embodiment of the presentinvention,

[0067]FIG. 5(A) being a partially-sectioned end view,

[0068]FIG. 5(B) an enlarged cross-sectional view of the essential partsin FIG. 5(A);

[0069]FIG. 6 is a diagram for explaining a load component F occurring ata contact position between a support ring and a trunnion in FIGS. 5(A)and 5(B);

[0070]FIG. 7 is a conceptual diagram showing a part of the powerrecirculation type tester used for the measurement of the induced thrustand slide resistance;

[0071]FIG. 8 is a chart showing the measurements of the induced thrustin the constant velocity universal joint of FIGS. 1(A)-1(C);

[0072]FIG. 9 is a chart showing the measurements of the slide resistancein the constant velocity universal joint of FIGS. 1(A)-1(C);

[0073]FIG. 10 is a partially-sectioned end view of a constant velocityuniversal joint according to a fourth embodiment of the presentinvention;

[0074]FIG. 1(A) is a longitudinal sectional view of the tripod memberand a roller assembly in the constant velocity universal joint of FIG.10, and

[0075]FIG. 11(B) is a plan view of the tripod member and the rollerassembly shown in FIG. 11(A);

[0076]FIG. 12 is an enlarged sectional view of a ring in the constantvelocity universal joint of FIG. 10;

[0077]FIG. 13(A) is a longitudinal sectional view showing the constantvelocity universal joint of FIG. 10 with an operating angle, and

[0078]FIG. 13(B) is a schematic side view of the tripod member in FIG.13(A);

[0079] FIGS. 14(A) and 14(B) show the dimensions of the individual partsof the constant velocity universal joint in FIG. 10,

[0080]FIG. 14(A) being a partially-sectioned end view,

[0081]FIG. 14(B) a longitudinal sectional view of the tripod member anda roller assembly;

[0082]FIG. 15 is a graph showing the results of pulsating torsionfatigue strength tests;

[0083] FIGS. 16(A)-16(C) show a tripod type constant velocity universaljoint according to a fifth embodiment of the present invention,

[0084]FIG. 16(A) being a partially-sectioned end view,

[0085]FIG. 16(B) a sectional view perpendicular to a trunnion in FIG.16(A),

[0086]FIG. 16(C) a sectional view of a support ring for explaining acontacting ellipse;

[0087]FIG. 17(A) is a longitudinal sectional view showing the constantvelocity universal joint of FIGS. 16(A)-16(C) with an operating angle,and

[0088]FIG. 17(B) is a schematic side view of the tripod member in FIG.17(A);

[0089] FIGS. 18(A)-18(C) show a tripod type constant velocity universaljoint according to a ninth embodiment of the present invention,

[0090]FIG. 18(A) being a partially-sectioned end view,

[0091]FIG. 18(B) a sectional view perpendicular to a trunnion in FIG.18(A),

[0092]FIG. 18(C) a longitudinal sectional view of the joint with anoperating angle;

[0093]FIG. 19 is an enlarged sectional view of a support ring in FIGS.18(A)-18(C);

[0094]FIG. 20 is an enlarged partial sectional view of a roller assemblyin FIGS. 16(A)-17(B);

[0095]FIG. 21 is an enlarged partial sectional view showing anotherconfiguration of the roller assembly;

[0096]FIG. 22 is a partial sectional view showing the tilt suppressingmeans in the tripod type constant velocity universal joint of FIGS.16(A)-16(C);

[0097]FIG. 23 is a partial sectional view showing the tilt suppressingmeans in a tripod type constant velocity universal joint according to asix embodiment of the present invention;

[0098]FIG. 24 is a partial sectional view showing the tilt suppressingmeans in a tripod type constant velocity universal joint according to aseventh embodiment of the present invention;

[0099]FIG. 25 is a partial sectional view showing the tilt suppressingmeans in a tripod type constant velocity universal joint according to aneighth embodiment of the present invention;

[0100]FIG. 26 is a partial sectional view showing a joint under no load;and

[0101]FIG. 27 is a partial sectional view explaining the production ofan inward component.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0102] Hereinafter, embodiments of the present invention will bedescribed.

[0103] FIGS. 1(A) through 2(B) show a first embodiment of the presentinvention. FIG. 1(A) shows a cross section of the joint, FIG. 1(B) asection perpendicular to a trunnion, and FIG. 1(C) a section of asupport ring. FIG. 2(A) shows a longitudinal section of the joint at anoperating angle (θ).

[0104] As shown in FIGS. 1(A)-1(C), the constant velocity universaljoint is chiefly composed of an outer joint member 10 and a tripodmember 20. One of two shafts to be coupled is connected to the outerjoint member 10, and the other is to the tripod member 20.

[0105] The outer joint member 10 has three track grooves 12 axiallyextending in its inner periphery. Each of the track grooves 12 hasroller guideways 14 formed on its circumferentially-opposed side walls.The tripod member 20 has three trunnions 22 which are projectedradially. Each of the trunnions 22 carries a roller 34, and this roller34 is accommodated in one of the track grooves 12 in the outer jointmember 10. The outer peripheries 34 a of the rollers 34 are convexsurfaces conformable to the roller guideways 14.

[0106] Here, the outer peripheries 34 a of the rollers 34 form convexsurfaces whose generators are arcs having the centers of curvatureradially off the axes of the trunnions 22. The roller guideways 14 havea section of Gothic-arch shape. Thus, the rollers 34 and the rollerguideways 14 make angular contact with each other. In FIG. 1(A),dot-dash lines show pairs of contact positions. Spherical outerperipheries of the rollers may be combined with tapered cross sectionsof the roller guideways 14 to achieve angular contact therebetween. Theadoption of such constitutions as provide angular contact between theouter peripheries 34 a of the rollers 34 and the roller guideways 14makes the rollers less prone to vibrate, thereby stabilizing theorientation of the rollers. Incidentally, when the angular contact isnot employed, the roller guideways 14 may be constituted, for example,by part of a cylindrical surface whose axis is parallel to that of theouter joint member 10. In this case, the cross-sectional shapes of theguideways 14 are arcs corresponding to the generator to the outerperipheries 34 a of the rollers 34.

[0107] Support rings 32 are fitted onto the outer peripheries 22 a ofthe trunnions 22. These support rings 32 and the rollers 34 areassembled (unitized) via a plurality of needle rollers 36 to constituteroller assemblies capable of relative rotations. More specifically, theneedle rollers 36 are rotatably interposed between inner and outerraceway surfaces, with the cylindrical outer peripheries of the supportrings 32 and the cylindrical inner peripheries of the rollers 34 as theinner and outer raceway surfaces, respectively. As shown in FIG. 1(B),the needle rollers 36 are loaded in as many as possible without anyretainer, or in a so-called full complement state. The referencenumerals 33 and 35 represent pairs of washers which are fitted toannular grooves formed in the inner peripheries of the rollers 34, withan aim to stop the needle rollers 36 from coming off.

[0108] In a longitudinal section {FIG. 1(A)}, the outer peripheries 22 aof the trunnions 22 have a straight shape parallel to the axes of thetrunnions 22. In a cross section {FIG. 1(B)}, the outer peripheries havethe shape of an ellipse whose major axis is perpendicular to the axis ofthe joint. The cross sections of the trunnions are generally elliptic,with a reduction in thickness as seen in the axial direction of thetripod member 20. In other words, each trunnion has such across-sectional shape that the faces opposed to each other in the axialdirection of the tripod member retreat toward each other, i.e., tosmaller diameters than the diameter of the imaginary cylindricalsurface.

[0109] The inner peripheries 32 c of the support rings 32 have anarcuate and convex section. That is, the generator to the innerperipheries 32 c is a convex arc having a radius of r {FIG. 1(C)}. Thiscombines with the above-described general elliptic cross sections of thetrunnions 22 and the provision of predetermined clearances between thetrunnions 22 and the support rings 32, to make the support rings 32movable along the axial directions of the trunnions 22 as well ascapable of tilting movements with respect to the trunnions 22. Besides,as described above, the support rings 32 and the rollers 34 areassembled (unitized) via the needle rollers 36 so as to be capable ofrelative rotations. Therefore, the support rings 32 and rollers 34 arecapable of unitary tilting movements with respect to the trunnions 22.Here, the term “tilting movements” refers to the tilts the axes of thesupport rings 32 and rollers 34 make with respect to the axes of thetrunnions 22, within the planes containing the axes of the trunnions 22{see FIG. 2(A)}.

[0110] In the embodiment shown in FIGS. 1(A)-1(C), the trunnions 22 havethe generally elliptic cross sections, and the inner peripheries 32 c ofthe support rings 32 have the arcuate convex cross sections. Thus, thecontacting ellipses therebetween approach points as shown by the brokenline in FIG. 1(c), with a reduction in area at the same time. As aresult, the forces to tilt the roller assemblies (32, 34, 36) decreasegreatly as compared to the conventional ones, whereby the rollers 34further improve in orientation stability. This means a reduction of theinduced thrust and of the slide resistance as well, accompanied with anarrowed range of variations of these values. Accordingly, in theconstant velocity universal joint of this embodiment, the specificationsof the induced thrust and slide resistance can be made smaller.Moreover, the joint can be accurately regulated within thespecifications.

[0111] In this embodiment, the tertiary rotational component of theinduced thrust under the condition (X1) {the number of revolutionsR=100-500 (rpm), the operating angle θ=0-14 (deg), and the load torqueT=0.1×Ts (N·m)} is regulated to or below 20 N (RMS). This provides theconstant velocity universal joint of this embodiment with a reduced andstabilized induced thrust, along with excellent low-vibrationcharacteristics and high reliability. FIG. 8 shows the measurements ofthe induced thrust (tertiary rotational component) in the constantvelocity universal joint of this embodiment, obtained by a tester to bedescribed later (FIG. 7).

[0112] While in this embodiment the tertiary rotational component of theinduced thrust in this embodiment is regulated to or below 20 N (RMS)under the condition (X1), it has only to be regulated to or below 30 N(RMS). Under the condition (X2) {the number of revolutions R=100-500(rpm), the operating angle θ=0-14 (deg), and the load torque T=0.2×Ts(N·m)}, the tertiary rotational component may be regulated to 55 N orless (RMS), and preferably 35 N or less (RMS). Under the condition (X3){the number of revolutions R=100-500 (rpm), the operating angle θ=0-14(deg), and the load torque T=0.3×Ts (N·m)}, it may be regulated to 80 Nor less (RMS), and preferably 55 N or less (RMS). In addition, theregulations under the conditions (X1), (X2), and (X3) may be effected tooverlap one another. Any one of these conditions may be used forregulation.

[0113] Moreover, in this embodiment, the slide resistance under thecondition (Y3) {the number of revolutions R=0 (rpm), the operating angleθ=0-10 (deg), the load torque T=98-196 (N·m), the vibrating frequencyf=15-40 (Hz), and the vibrating amplitude=±0.10 to ±0.25 (mm)} isregulated to or below 80 N (peak to peak), aside from the induced thrustregulation described above. This provides the constant velocityuniversal joint of this embodiment with reduced, stabilized inducedthrust and slide resistance, along with excellent low-vibrationcharacteristics and high reliability. FIG. 9 shows the measurements ofthe slide resistance in the constant velocity universal joint of thisembodiment, obtained by the tester to be described later (FIG. 7).

[0114] Note that the slide resistance may be regulated to 40 N or less(peak to peak) under the condition (Y1) {the number of revolutions R=0(rpm), the operating angle θ=0-10 (deg), the load torque T=98-196 (N·m),the vibrating frequency f=15-40 (Hz), and the vibrating amplitude=±0.01to ±0.03 (mm)}. It may be regulated to 60 N or less (peak to peak) underthe condition (Y2) {the number of revolutions R=0 (rpm), the operatingangle θ=0-10 (deg), the load torque T=98-196 (N·m), the vibratingfrequency f=15-40 (Hz), and the vibrating amplitude=±0.05 to ±0.08(mm)}. Here, an appropriate condition is selected from among theabove-mentioned three conditions based on the vibrating amplitude withreference to the amplitude of external vibrations input to the constantvelocity universal joint, such as idling vibrations. In some cases, avalue other than those in the above-mentioned three conditions can beused for the vibrating amplitude. Furthermore, even though both theinduced thrust and the slide resistance are regulated in thisembodiment, either one of these may be regulated alone.

[0115] The regulations of the induced thrust and the slide resistancecan be effected, for example, through 100% control. Alternatively, theregulations can be effected by sampling a predetermined number ofproducts out of finished product lots at a predetermined frequency,measuring the samples for induced thrust and slide resistance, andcontrolling the lots to which the samples belong to based on themeasurements.

[0116]FIG. 7 shows a part of the power recirculation type tester to beused for the measurement of the induced thrust and slide resistance. Inthe diagram, the tripod type constant velocity universal joint of theabove-described embodiment is placed on the A side (hereinafter,referred to as “A-side joint”). A pairing constant velocity universaljoint of fixed type (for example, a Rzeppa type constant velocityuniversal joint) is arranged on the B side (hereinafter, referred to as“B-side joint”). The tripod member of the A-side joint and the innerjoint member of the B-side joint are coupled to each other via anintermediate shaft. A predetermined operating angle θ is given to boththe joints. In addition, the outer joint member of the A-side joint isconnected to a load cell. The outer joint member of the B-side joint isconnected to a hydraulic servo.

[0117] For induced thrust measurement, a load torque T with apredetermined number of revolutions R and magnitude is input to theB-side joint. This load torque T is transferred from the B-side jointthrough the intermediate shaft to the A-side joint, whereby the A-sidejoint rotates at the same number of revolutions as the input number ofrevolutions. Here, an induced thrust occurs in the A-side joint. Thisinduced thrust is detected by the load cell through the outer jointmember of the A-side joint. Incidentally, the hydraulic servo is notactuated in measuring the induced thrust.

[0118] The induced thrust is measured, for example, at a predeterminednumber of rotations R (=100-500 rpm) and load torque T (=0.1×Ts N·m,0.2×Ts N·m, 0.3×Ts N·m) while changing the operating angle θ to 4, 6, 8,10, 12, and 14 deg, for five minutes on each operating angle. Then, themeasurement data under each measurement condition is subjected tofrequency analysis. The tertiary rotational components obtained are usedfor induced thrust regulation and control.

[0119] Meanwhile, for slide resistance measurement, the rotation of thetester is stopped. Then, the B-side joint and the A-side joint are putunder a predetermined torque T while the hydraulic servo is activated toinput an axial vibrating force having a predetermined amplitude to theB-side joint. This axial vibrating force is transferred from the B-sidejoint through the intermediate shaft to the tripod member of the A-sidejoint, and further transmitted to the outer joint member of the A-sidejoint by means of the internal slide resistance. As a result, the outerjoint member of the A-side joint vibrates with the slide resistance asthe vibratory force. This vibratory force (slide resistance) is detectedby the load cell.

[0120] The slide resistance is measured, for example, at a predeterminedload torque T (=98-196 N·m), vibrating frequency f (=15-40 Hz), andvibrating amplitude (±0.01 to ±0.03 mm, ±0.05 to ±0.08 mm, ±0.10 to±0.25 mm) while changing the operating angle θ to 6, 8, and 10, for 1-5minute(s) on each operating angle. Then, the absolute values of thepositive and negative peak values in the measurement data (waveform)under each measurement condition are totaled (peak to peak). The valuesobtained are used for slide resistance regulation and control.

[0121] In addition to the regulations and controls by the sampling andmeasurements described above, there may be provided means forindividually regulating and controlling the dimensions and shapes ofparts that are associated with the induced thrust and/or slideresistance (e.g., for individually regulating the outer peripheries ofthe trunnions of the tripod member, the contact surfaces of the rollers,the contact surfaces of the support rings, the contact surfaces of theneedle rollers, the roller guideways of the outer joint member, and soforth in dimension and shape). Moreover, means for individuallyregulating and controlling the factors contributing to the rotationalstability of the rollers in the roller assemblies (e.g., forindividually regulating the radial and axial clearances between parts,the surface properties of the contact surfaces, the lubricationconditions, and so forth) may also be provided.

[0122] FIGS. 3(A) through 4 show a second embodiment of the presentinvention. This second embodiment differs from the above-described firstembodiment only in that the generator to the inner peripheries 32 c ofthe support rings 32, which has been a single arc in the firstembodiment, consists of a combination of an arc portion 32 a at thecenter and relief portions 32 b on both sides. The role of the reliefportions 32 b is to avoid the interference with the trunnions 22 at anoperating angle (θ) as shown in FIG. 3(C). Each relief portion 32 b isformed by a straight or curved line that gradually spreads out from anedge of the arc portion 32 a to an end of the support ring 32. Therelief portions 32 b illustrated here are formed by part of a conicalsurface having a vertex angle α=50°. The arc portions 32 a have a largeradius of curvature (r) on the order of e.g. 30 mm, so as to allow thetrunnions 20 to tilt 2-3° or so with respect to the support rings 32. Intripod type constant velocity universal joints, one rotation of theouter joint member 10 constitutionally produces three nutations of thetripod member 20 about the center of the outer joint member 10. Here,the amount of eccentricity represented by the symbol e {FIG. 2(A)}increases in proportion to the operating angle (θ). While the threetrunnions 22 are spaced by 120° from one another, the presence of theoperating angle (θ) causes the trunnions 22 to tilt as shown in FIG.2(B). More specifically, with reference to the vertical trunnion 22shown to the upper in the diagram, the remaining two trunnions 22 aredeclined slightly from their zero-operating-angle axes shown by thedot-dash lines. For example, an operating angle (θ) of approximately 23°causes a decline of the order of 2-3°. This decline can be readilyallowed by the curvature of the arc portions 32 a on the innerperipheries 32 c of the support rings 32. Therefore, the surfacepressures at the contact portions between the trunnions 22 and thesupport rings 32 can be prevented from becoming excessively high.Incidentally, FIG. 2(B) is a schematic representation of the threetrunnions 22 of the tripod member 20 as seen from the left side of FIG.2(A), the full lines showing the individual trunnions.

[0123] This second embodiment is identical to the first embodiment inthat the tertiary rotational component of the induced thrust isregulated to or below 20 N (RMS) under the condition (X1) and the slideresistance is regulated to or below 80 N (peak to peak) under thecondition (Y3). Incidentally, since the measurements showed the similartendencies as those in the first embodiment, description thereof will beomitted here. Besides, the regulation conditions for the induced thrustand slide resistance, and the effects thereof are in conformity withthose of the first embodiment described above. Thus, repetitivedescription thereof will be omitted.

[0124] FIGS. 5(A) through 6 show a third embodiment of the presentinvention. Here, FIGS. 5(A) and 5(B) show the joint at an operatingangle of 0°, under no rotational torque.

[0125] The tripod type constant velocity universal joint in thisembodiment includes an outer joint member 1 to be connected to one oftwo shafts to be coupled, and a tripod member 2 to be connected to theother.

[0126] The outer joint member 1 is generally cup-like in appearance, andhas an inner periphery provided with three axially-extending trackgrooves 1 a at circumferential regular positions. Each of the trackgrooves la has roller guideways 1 a 1 on both sides.

[0127] The tripod member 2 has three radially-projecting trunnions 2 aat circumferential regular positions. Each of the trunnions 2 a has aconvex-arcuate outer periphery 2 a 1. Onto the outer periphery 2 a 1 ismounted a roller assembly A, or an assembly of a support ring 3, aplurality of needle rollers 4, and a roller 5.

[0128] As magnified in FIG. 5(B), each roller assembly A includes theplurality of needle rollers 4 rotatably interposed between a cylindricalouter periphery 3 a of the support ring 3 and a cylindrical innerperiphery 5 a of the roller 5. A pair of snap rings 6 fitted to theinner periphery 5 a of the roller 5 lock the support ring 3 and theneedle rollers 4 at both ends so as to restrain axial movements of thesupport ring 3 and the needle rollers 4 with respect to the roller 5(movements along the axis Z of the trunnion 2 a). The end faces of thesupport ring 3 and the end faces of the needle rollers 4 have axialclearances δ from the pair of snap rings 6. In the diagram, the axialclearances δ are rather exaggerated in dimension. Moreover, the axialclearances between the end faces of the support ring 3 and the snaprings 6 and the axial clearances between the end faces of the needlerollers 4 and the snap rings 6 can be designed in identical values or indifferent values. In the diagrams, both the clearances are shown as anaxial clearance δ without distinction. Furthermore, the outer periphery3 a of the support ring 3 and the inner periphery Sa of the roller 5have slight radial clearances from the rolling contact surfaces of theneedle rollers 4.

[0129] The inner peripheries 3 b of the support rings 3 are fitted tothe spherical outer peripheries 2 a 1 of the trunnions 2 a. In thisembodiment, the inner peripheries 3 b of the support rings 3 have theform of a cone gradually contracting in diameter toward the extremitiesof the trunnions 2 a. The inner peripheries 3 b make line contact withthe outer peripheries 2 a 1 of the trunnions 2 a. This permits tiltingmovements of the roller assemblies A with respect to the trunnions 2 a.The inner peripheries 3 b of the support rings 3 have an inclination aas small as e.g. 0.1-3°, and preferably 0.1-1°. The present embodimentemploys the setting of α=0.5°. In the diagrams, the inclinations of theinner peripheries 3 b are rather exaggerated.

[0130] The generator to the outer peripheries 5 b of the rollers 5 arearcs whose centers are outwardly off the centers of the trunnions 2 a.

[0131] In the present embodiment, the roller guideways 1 a 1 in theouter joint member 1 have a section of double-arc shape (Gothic-archshape). Therefore, the roller guideways lal and the outer periphery 5 bof each roller 5 make angular contact at two points p and q. The angularcontact points p and q are opposed to each other in the direction of theaxis Z of the trunnion 2 a, at equal distances from the center line thatpasses through the center of the outer periphery 5 b of the roller 5 andintersects the axis Z at right angles. Incidentally, the rollerguideways 1 a 1 may have a section of V shape, parabola shape, or thelike. Moreover, in this embodiment, shoulder surfaces 1 a 2 are arrangedin the track grooves 1 a next to the roller guideways 1 a 1, so that theend faces 5 c of the rollers 5 on the trunnion-extremity sides areguided by these shoulder surfaces 1 a 2.

[0132] Since the inner peripheries 3 b of the support rings 3 are shapedlike a cone that gradually contracts in diameter toward the trunnionextremity, the application of rotational torque to this joint producesload components F as shown in FIG. 6 (where the inclination of the innerperiphery 3 b is exaggerated more than in FIGS. 5(A) and 5(B)). Morespecifically, load components F directed to the trunnion extremitiesoccur at the contact positions S between the inner peripheries 3 b ofthe support rings 3 and the outer peripheries 2 a 1 of the trunnions 2a. These load components F act to push up the support rings 3 and theneedle rollers 4 toward the trunnion extremities, so that the supportrings 3 and the needle rollers 4 are pressed against the snap rings 6 onthe trunnion-extremity sides. This stabilizes the contact positions Sbetween the inner peripheries 3 b of the support rings 3 and the outerperipheries 2 a 1 of the trunnions 2 a. Besides, the load components Falso act to push up the rollers 5 toward the trunnion extremities viathe support rings 3 and the needle rollers 4, thereby stabilizing theorientation of the rollers 5 with respect to the roller guideways 1 a 1.such stabilization of the contact positions S and the orientationstabilization of the rollers 5 combine with each other to reduce theinduced thrust and the slide resistance, as well as to narrow the rangeof variations of these values. Accordingly, in the constant velocityuniversal joint of this embodiment, the specifications of the inducedthrust and slide resistance can be made smaller. Moreover, the joint canbe accurately regulated within the specifications. Incidentally, theinner peripheries 3 b of the support rings 3 may have a cylindricalshape.

[0133] The regulations of the induced thrust and slide resistance, andthe effects therefrom are in conformity with those of the firstembodiment described above. Thus, repetitive description thereof will beomitted.

[0134] Note that the present invention in association with theregulations of the induced thrust and slide resistance is not limited tothe constant velocity universal joints having the configurationsdescribed above, and may be applied to constant velocity universaljoints of other configurations.

[0135] Next, a fourth embodiment of the present invention will bedescribed with reference to FIGS. 10 through 13(B). Here, FIG. 10 is apartially-sectioned end view of a constant velocity universal joint.FIG. 11(A) is a longitudinal sectional view of a tripod member and aroller assembly in the constant velocity universal joint shown in FIG.10. FIG. 11(B) is a plan view of FIG. 11(A). FIG. 12 is an enlargedsectional view of a ring. FIG. 13(A) is a longitudinal sectional view ofthe constant velocity universal joint at an operating angle.

[0136] As shown in FIG. 10, the constant velocity universal jointincludes an outer joint member 10 and a tripod member 20. One of twoshafts to be coupled is connected to the outer joint member 10, and theother is to the tripod member 20.

[0137] The outer joint member 10 has three track grooves 12 axiallyextending in its inner periphery. Each of the track grooves 12 hasroller guideways 14 formed on its circumferentially-opposed side walls.The tripod member 20 has three trunnions 22 which are projectedradially. Each of the trunnions 22 carries a roller 34, and this roller34 is accommodated in one of the track grooves 12 in the outer jointmember 10. The outer peripheries of the rollers 34 are convex surfacesconforming to the roller guideways 14. The tripod member 20 has a splinehole (or serration hole) 24 for accepting a spline shaft portion (orserration shaft portion) of the shaft to be coupled.

[0138] The outer periphery of each roller 34 forms a convex surfacewhose generator is an arc having the center of curvature radially offthe axis of the trunnion 22. The roller guideways 14 have a section ofGothic-arch shape. Thus, the rollers 34 and the roller guideways 14 makeangular contact with each other. Spherical outer peripheries of therollers may be combined with tapered cross sections of the rollerguideways 14 to achieve angular contact therebetween. The adoption ofsuch constitutions as provide angular contact between the outerperipheries 34 a of the rollers 34 and the roller guideways 14 makes therollers 34 less prone to vibrate, thereby stabilizing the orientation ofthe rollers. Incidentally, when the angular contact is not employed, theroller guideways 14 may be constituted, for example, by part of acylindrical surface whose axis is parallel to that of the outer jointmember 10. In this case, the cross-sectional shapes of the guideways 14are arcs corresponding to the generator to the outer peripheries of therollers 34.

[0139] Rings 32 are fitted onto the outer peripheries of the trunnions22. These rings 32 and the rollers 34 are assembled (unitized) via aplurality of needle rollers 36 to constitute roller assemblies capableof relative rotations. More specifically, the needle rollers 36 arerotatably interposed between inner and outer raceway surfaces, with thecylindrical outer peripheries of the rings 32 and the cylindrical innerperipheries of the rollers 34 as the inner and outer raceway surfaces,respectively. The needle rollers 36 are loaded in as many as possiblewithout any retainer, or in a so-called full complement state. In thisembodiment, collars 35 for receiving the end faces of the needle rollers36 b are formed on one ends of the rollers 34. The reference numeral 33represents washers which are fitted to annular grooves formed in theinner peripheries of the rollers 34, with an aim to stop the needlerollers 36 from coming off. These washers 33 have a cut across theircircumferences {see FIG. 11(B)}, so as to be fitted to the annulargrooves in the inner peripheries of the rollers 34 as elasticallycontracted in diameter. Incidentally, the collars 35 may be eliminatedso that both ends of the needle rollers 34 are retained by pairs ofwashers 33.

[0140] In this embodiment, the outer peripheries 22 a of the trunnions22, as seen in a longitudinal section {see FIG. 11(A)}, have a straightshape parallel to the axes of the trunnions 22. In a cross section {FIG.11(B)}, the outer peripheries have the shape of an ellipse whose majoraxis is perpendicular to the axis of the constant velocity universaljoint. In FIG. 11(B), the symbols a and b represent the major radius andthe minor radius, respectively. The cross sections of the trunnions 22are generally elliptic, with a reduction in thickness as seen in theaxial direction of the tripod member 20. In other words, each trunnionhas such a cross-sectional shape that the faces opposed to each other inthe axial direction of the tripod member retreat toward each other,i.e., to smaller diameters than the diameter of the imaginarycylindrical surface.

[0141] As shown in FIG. 12, the generator to the inner peripheries ofthe rings 32 consists of a combination of an arc portion 32 a at thecenter and relief portions 32 b on both sides. The role of the reliefportions 32 b is to avoid the interference with the trunnions 22 at anoperating angle θ as shown in FIG. 13(A). Each relief portion 32 b isformed by a straight or curved line that gradually spreads out from anedge of the arc portion 32 a to an end of the ring 32. The reliefportions 32 b illustrated here are formed by part of a conical surfacehaving a vertex angle α=50°. The arc portions 32 a have a large radiusof curvature on the order of e.g. 30 mm, so as to allow the trunnions 20to tilt 2-3° or so with respect to the rings 32. Here, instead of beingprovided with the relief portions 32 b as in this embodiment, the innerperipheries of the rings 32 may be formed into arcuate convex sectionsalong their entire lengths. In either case, the above-described generalelliptic cross sections of the trunnions 22 and the provision ofpredetermined clearances between the trunnions 22 and the rings 32combine with each other to make the rings 32 movable along the axialdirections of the trunnions 22 as well as capable of tilting movementswith respect to the trunnions 22. Besides, as described above, the rings32 and the rollers 34 are unitized via the needle rollers 36 so as to becapable of relative rotations. Therefore, the rings 32 and rollers 34are capable of unitary tilting movements with respect to the trunnions22. Here, the term “tilting movements” refers to the tilts the axes ofthe rings 32 and rollers 34 make with respect to the axes of thetrunnions 22, within the planes containing the axes of the trunnions 22{see FIG. 13(A)}.

[0142] In the case of a conventional joint, the trunnions make contactwith the inner peripheries of the rings at the full lengths of theirouter peripheries. This produces circumferentially extended contactingellipses. Therefore, when the trunnions tilt with respect to the outerjoint member, there arise friction moments which function to tilt therings, and finally the rollers, with the movement of the trunnions. Onthe other hand, in the embodiment shown in FIG. 10, the trunnions 22have the generally elliptic cross sections and the inner peripheries ofthe rings 32 have the spherical cross sections. Thus, the contactingellipses therebetween approach points as shown by the broken line inFIG. 12, with a reduction in area at the same time. As a result, theforces to tilt the roller assemblies (32, 34, 36) decrease greatly ascompared to the conventional ones, whereby the rollers 34 furtherimprove in orientation stability. Moreover, in a conventional joint, thetrunnions and the rings come to contact with each other at the widthcenters of the rings when the operating angle θ=0. When the jointtransfers torque with some operating angle, however, the trunnionsoscillate axially, shifting the contacts between the trunnions and therings to the lower than the width centers of the rings. This leads tounstable behavior of the needle rollers, sometimes hampering theirstable rolling. In the embodiment shown in FIG. 10, on the contrary, thecontacts between the trunnions and the inner peripheries of the ringsalways stay at the width centers of the rings 32. Thus, the needlerollers 36 roll with stability.

[0143] In tripod type constant velocity universal joints, one rotationof the outer joint member 10 constitutionally produces three nutationsof the tripod member 20 about the center of the outer joint member 10.Here, the amount of eccentricity of the trunnion center about the centerof the outer joint member 10, represented by the symbol e {FIG. 13(A)},increases in proportion to the operating angle θ. While the threetrunnions 22 are spaced by 120° from one another, the presence of theoperating angle θ causes the trunnions 22 to tilt as shown in FIG.13(B). More specifically, with reference to the vertical trunnion 22shown to the upper in the diagram, the remaining two trunnions 22 aredeclined slightly from their axes at the operating angle θ=0, shown bythe dot-dash lines. For example, an operating angle θ of approximately23° causes a decline of the order of 2-3°. This decline can be readilyallowed by the curvature of the arc portions 32 a on the innerperipheries of the rings 32. Therefore, the surface pressures at thecontact portions between the trunnions 22 and the rings 32 can beprevented from becoming excessively high. Incidentally, FIG. 13(B) is aschematic representation of the three trunnions 22 of the tripod member20 as seen from the left side of FIG. 13(A), the full lines showing theindividual trunnions. Moreover, clearances for absorbing the tilts ofthe trunnions 22 resulting from such nutations of the trunnion center,which is peculiar to tripod type constant velocity universal joints, areprovided between the major axes 2 a of the trunnions 22 and the innerdiameters of the rings 32.

[0144] Conventional joints have collars for restraining roller tilts.These collars are formed on the bottom sides of the track grooves, i.e.,on the sides of greater diameter as seen in the cross section of theouter joint member, so as to be opposed to the end faces of the rollers.The constant velocity universal joints according to the presentinvention may also have such collars. Nevertheless, in the embodimentsdescribed above, the factors to tilt the rollers 34 are removed, orsuppressed as much as possible. Accordingly, such collars in the trackgrooves 12 are not always required, and thus are omitted. Thiseliminates the fear that the rollers 34 might come into contact with thecollars to produce sliding frictions when they are temporarily swung bysome reason.

[0145] Now, the dimensional proportion of the individual parts of theconstant velocity universal joint according to the embodiment shown inFIG. 10 will be described with reference to FIGS. 14(A) and 14(B). Thefollowing provides the description of the individual symbols in thediagrams.

[0146] S_(PCD): the pitch circle diameter of the spline hole 24 in thetripod member 20,

[0147] H_(T): the barrel width of the tripod member 20,

[0148] D_(JL): the major diameter of a trunnion 22,

[0149] D_(O): the outer diameter of the outer joint member 10,

[0150] T_(PCD): the pitch circle diameter of the track grooves 12,

[0151] D_(R): the outer diameter of a roller 34,

[0152] H_(R): the with of a roller 34, and

[0153] R_(R): the radius of curvature of the outer periphery of a roller34.

[0154] The pitch circle diameter T_(PCD) of the track grooves 12 in theouter joint member 10 is set so that its ratio to the pitch circlediameter S_(PCD) of the spline hole 24 in the tripod member 20, orT_(PCD)/S_(PCD), falls within the range of 1.7-2.1, or preferably1.72-2.10. The reason for this is that if the track grooves 12 are madeso small in pitch circle diameter T_(PCD) that the ratio T_(PCD)/S_(PCD)falls below 1.72, there arises a problem of interference between therollers 34 and the shoulders of the trunnions 22. Besides, the surfacepressures at the contact portions, such as between the trunnions 22 andthe rings 32, increase to cause a drop in durability. On the other hand,if the track grooves 12 are made so large in pitch circle diameterT_(PCD) that the ratio T_(PCD)/S_(PCD) exceeds 2.10, the outer jointmember 10 increases in outer diameter D_(O) with a deterioration invehicle mountability. In addition, if the outer diameter D_(O) of theouter joint member 10 is given, there remains little space for theroller assemblies (32, 34, 36).

[0155] In order to verify the durability mentioned above, durabilitytests were conducted on constant velocity universal joints withT_(PCD)/S_(PCD) set at the values shown in the top row of Table 1. Theresults are shown in the middle row of Table 1. The mark ∘ indicatesthat the target time was satisfied. The mark Δ indicates that the targettime was not satisfied. The following shows the test conditions.

[0156] Torque: 686 Nm,

[0157] Number of revolutions: 250 rpm,

[0158] Operating angle: 10 deg, and

[0159] Operating hours: 300 hrs.

[0160] As shown in the middle row of Table 1, it is confirmed that thejoint of 1.6 in T_(PCD)/S_(PCD) could not satisfy the target time whilethose of 1.7 or higher in T_(PCD)/S_(PCD) satisfied the target time,with sufficient durability.

[0161] Moreover, with T_(PCD)/S_(PCD) set at the individual valuesdescribed above, the outer joint members 10 were checked for a need ofan increase in outer diameter. The results are shown in the bottom rowof Table 1. While the outer joint members of 2.1 or lower inT_(PCD)/S_(PCD) were in no need of an increase in outer diameter, thatof 2.2 in T_(PCD)/S_(PCD) needed an increase in outer diameter.

[0162] The major diameter D_(JL) of a trunnion 22 is set so that itsratio to the pitch circle diameter S_(PCD) of the spline hole 24, orD_(JL)/S_(PCD), falls within the range of 0.6-1.0, or preferably0.63-0.94. The reason for this is that if the trunnions are made sosmall in major diameter DJL that the ratio D_(JL)/S_(PCD) falls below0.6, the constant velocity universal joint cannot function satisfactory.On the other hand, if the trunnions are made so large in major diameterthat the ratio D_(JL)/S_(PCD) exceeds 1.0, there remains little spacefor the roller assemblies to be arranged in, which is dissatisfactory interms of the limit in the outer diameter. Here, pulsating torsionfatigue strength tests were conducted on four types of test joints whichwere the constant velocity universal joints according to the embodimentof FIG. 10, with the major diameter D_(JL) of the trunnions 22 changedto set the ratio D_(JL)/S_(PCD) to the pitch circle diameter of thespline hole 24 was set at “0.5,” “0.6,” “0.7,” and “1,” respectively.FIG. 15 shows the test results. The abscissa represents the number ofrepetitions up to breakage (N), and the ordinate the load torque (T).The dot-dashed “0.6”, line is in close agreement with the target T-Nchart. Thus, the ratio of “0.5” precludes satisfactory joint functions.On the other hand, the ratios above “1.0” eliminates the space for theroller assemblies to be arranged in, which is dissatisfactory in termsof the limit in the outer diameter.

[0163] The outer diameter D_(R) of the rollers 34 is set so that itsratio to the pitch circle diameter S_(PCD) of the spline hole 24, orD_(R)/S_(PCD), falls within the range of 1.4-2.3, or preferably1.47-2.21. If the rollers 34 are made so small in outer diameter D_(R)that the ratio D_(R)/S_(PCD) falls below 1.47, the surface pressuresbetween the rollers 34 and the roller guideways 14 increase to drop thedurability. Besides, the reduction in the thickness of the rollers 34causes a problem of deteriorated strength. Meanwhile, when the rollers34 are made so large in outer diameter D_(R) that the ratioD_(R)/S_(PCD) exceeds 2.21, the outer joint member 10 becomes thinner todrop in forgeability if the diameter D_(O) of the outer joint member 10is given. This also produces a problem of shaft interference, as well asadvances interference of the outer joint member 10 with the cup bottoms,yielding an increased cup depth and a greater weight.

[0164] In order to verify the durability mentioned above, durabilitytests were conducted on constant velocity universal joints withD_(R)/S_(PCD) set at the values shown in the top row of Table 2. Theresults are shown in the middle row of Table 2. The test conditions wereidentical to those for Table 1. Again, the mark ∘ indicates that thetarget time was satisfied. The mark Δ indicates that the target time wasnot satisfied. Note that the portions to be evaluated in this case arethe rollers/roller guideways.

[0165] As shown by the test results in the middle row, it is confirmedthat the joint of 1.3 in D_(R)/S_(PCD) could not satisfy the target timewhile those of 1.48 or higher in D_(R)/S_(PCD) satisfied the targettime, with sufficient durability.

[0166] Additionally, evaluations as to the forgeability of the outerjoint members are shown in the bottom row of Table 2. More specifically,thinner portions of the outer joint members were checked for cracks. Theouter joint member of 2.33 in D_(R)/S_(PCD) produced some cracks,whereas those of 2.21 or lower in D_(R)/S_(PCD) were free of cracks,with no sign of poor forgeability.

[0167] The outer diameter D_(O) of the outer joint member 10 is set sothat its ratio to the pitch circle diameter S_(PCD) of the spline hole24, or D_(O)/S_(PCD), falls within the range of 2.78-3.77. If the outerjoint member 10 is made so small in outer diameter D_(O) that the ratioD_(O)/S_(PCD) falls below 2.78, the surface pressures at the individualcontact portions increase to lower the durability. In addition, thestresses on the individual parts increase to cause deterioration instrength. On the other hand, increasing the outer diameter D_(O) of theouter joint member 10 to such an extent that the ratio D_(O)/S_(PCD)exceeds 3.77 not only deteriorates the vehicle mountability but alsoyield a weight increase.

[0168] The barrel width H_(T) of the tripod member 20 is set so that itsratio to the pitch circle diameter S_(PCD) of the spline hole 24, orH_(T)/S_(PCD), falls within the range of 0.81-1.22. If the tripod member20 is made so small in barrel width H_(T) that the ratio H_(T)/S_(PCD)falls below 0.81, the length of the spline fit decreases to lower thespline strength. On the other hand, if the tripod member 20 is made solarge in barrel width H_(T) that the ratio H_(T)/S_(PCD) exceeds 1.22,there arises a problem of interference between the rollers 34 and theshoulders of the trunnions 22.

[0169] The width H_(R) of the rollers 34 is set so that its ratio to thepitch circle diameter S_(PCD) of the spline hole 24, or H_(R)/S_(PCD),falls within the range of 0.38-0.67. If the rollers 34 are made so smallin width H_(R) that the ratio H_(R)/S_(PCD) falls below 0.38, thesurface pressures between the rollers 34 and the roller guideways 14increase to drop the durability. Besides, the reduction in the rigidityof the rollers 34 results in insufficient strength. Meanwhile, when therollers 34 are made so large in width H_(R) that the ratio H_(R)/S_(PCD)exceeds 0.67, the rollers 34 come into interference with the shouldersof the trunnions 22. Moreover, if the outer diameter D_(O) of the outerjoint member 10 is given, the outer joint member 10 becomes thinner todrop in forgeability.

[0170] The radius of curvature R_(R) of the outer peripheries of therollers 34 is set so that its ratio to the pitch circle diameter S_(PCD)of the spline hole 24, or R_(R)/S_(PCD), falls within the range of0.19-1.11. If the outer peripheries of the rollers 34 are made so smallin the radius of curvature R_(R) that the ratio R_(R)/S_(PCD) fallsbelow 0.19, the rollers 34 drop in rigidity into insufficient strength.Meanwhile, when the outer peripheries of the rollers 34 are made solarge in the radius of curvature R_(R) that the ratio R_(R)/S_(PCD)exceeds 1.11, the outer joint member 10 becomes thinner to drop inforgeability if the diameter D_(O) of the outer joint member 10 isgiven.

[0171] FIGS. 16(A) through 17(B) show a tripod type constant velocityuniversal joint according to a fifth embodiment. FIG. 16(A) shows asection perpendicular to the axis of the joint. FIG. 16(B) shows asection perpendicular to the axis of a trunnion. FIG. 16(C) shows asection of a support ring. FIGS. 17(A) and 17(B) show the joint with anoperating angle (θ), in a section parallel to the axis of the joint.

[0172] As shown in FIG. 16(A), the constant velocity universal joint ofthis embodiment is chiefly composed of an outer joint member 10 and atripod member 20. One of two shafts to be coupled is connected to ashaft portion 10 a {see FIG. 17(A)} of the outer joint member 10, andthe other is to the tripod member 20.

[0173] The outer joint member 10 has three track grooves 12 axiallyextending in its inner periphery. Each of the track grooves 12 hasroller guideways 14 formed on its circumferentially-opposed side walls.The tripod member 20 has three trunnions 22 which are projectedradially. Each of the trunnions 22 carries a roller 34, and this roller34 is accommodated in one of the track grooves 12 in the outer jointmember 10. The outer peripheries 34 a of the rollers 34 are convexsurfaces conformable to the roller guideways 14.

[0174] Here, the outer peripheries 34 a of the rollers 34 have arcuateconvex sections whose generators are arcs having the centers ofcurvature radially off the axes of the trunnions 22. The rollerguideways 14 have a section of Gothic-arch shape. Thus, the rollers 34and the roller guideways 14 make angular contact with each other.Incidentally, spherical outer peripheries of the rollers may be combinedwith tapered, parabolic, or other cross sections of the roller guideways14 to achieve angular contact therebetween. The adoption of suchconstitutions as provide two angular contacts between the outerperipheries 34 a of the rollers 34 and the roller guideways 14stabilizes the orientation of the rollers. Incidentally, when theangular contact is not employed, the roller guideways 14 may beconstituted, for example, by part of a cylindrical surface whose axis isparallel to that of the outer joint member 10. In this case, thecross-sectional shapes of the guideways 14 are arcs corresponding to thegenerator to the outer peripheries 34 a of the rollers 34.

[0175] A support ring 32 is fitted onto the outer periphery 22 a of eachtrunnion 22. These support rings 32 and the rollers 34 are assembled(unitized) via a plurality of needle rollers 36 to constitute rollerassemblies (roller assemblies) A capable of relative rotations.

[0176] More specifically, as magnified in FIG. 20, a plurality of needlerollers 36 are rotatably interposed between inner and outer racewaysurfaces, with the cylindrical outer peripheries of the support rings 32and the cylindrical inner peripheries of the rollers 34 as the inner andouter raceway surfaces, respectively. Then, lock means are arranged onboth axial sides of each roller assembly A so as to restrain axialrelative movements of the support rings 32, the rollers 34, and theneedle rollers 36. In the example shown in the diagram, the lock meanson both sides consist of the lock rings 33 and 35, which are fitted tocircumferential grooves 34 c and 34 d formed in the bore ends of theroller 34, respectively. There are slight axial clearances in betweenthe lock rings 33, 35 and the support ring 32, and in between the lockrings 33, 35 and the needle rollers 36. The lock rings 33 and 35 thusattached to the rollers 34 make contact with the end faces of thesupport rings 32 and the end faces of the needle rollers 36, therebyrestraining these members from axial relative movements with respect tothe rollers 34. Here, an example of the lock rings 33 and 35 is a splitring partially split by a slit. As shown in FIG. 16(B), the needlerollers 36 are loaded in as many as possible without any retainer, or ina so-called full complement state.

[0177] Alternatively, the roller assemblies A may adopt the structureshown in FIG. 21. In this example, one of the lock means in a rollerassembly A consists of the lock ring 33, and the other consists of alock collar 34 e. The lock ring 33 is attached by fitting to acircumferential groove 34 c formed in one of the bore ends of the roller34. The lock collar 34 e is arranged integrally on the other end of theroller 34. As compared with the structure shown in FIG. 20, there is anadvantage that assembling tolerance due to the lock-ring constitution ofthe other lock means can be eliminated to reduce the axial clearances tothe support ring 32 and the needle rollers 36 by half.

[0178] In a longitudinal section {FIG. 16(A)}, the outer peripheries 22a of the trunnions 22 have a straight shape parallel to the axes of thetrunnions 22. In a cross section {FIG. 16(B)}, the outer peripherieshave the shape of an ellipse whose major axis is perpendicular to theaxis of the joint. The cross sections of the trunnions are generallyelliptic, with a reduction in thickness as seen in the axial directionof the tripod member 20. In other words, each trunnion has such across-sectional shape that the faces opposed to each other in the axialdirection of the tripod member retreat toward each other, i.e., tosmaller diameters than the diameter of the imaginary cylindricalsurface.

[0179] The inner peripheries 32 c of the support rings 32 have anarcuate and convex section. That is, the generator to the innerperipheries 32 c is a convex arc having a radius of r {FIG. 16(C)}. Thiscombines with the above-described general elliptic cross sections of thetrunnions 22 and the provision of predetermined clearances between thetrunnions 22 and the support rings 32, to make the support rings 32movable along the axial directions of the trunnions 22 as well ascapable of tilting movements with respect to the trunnions 22. Besides,as described above, the support rings 32 and the rollers 34 areassembled via the needle rollers 36 so as to be capable of relativerotations (the roller assemblies A). Therefore, the support rings 32 androllers 34 are capable of unitary tilting movements with respect to thetrunnions 22. Here, the term “tilting movements” refers to the tilts theaxes of the support rings 32 and rollers 34 (the axes of the rollerassemblies A) make with respect to the axes of the trunnions 22, withinthe planes containing the axes of the trunnions 22.

[0180] As described above, in the constant velocity universal joint ofthis embodiment, the trunnions 22 have the generally elliptic crosssections, and the inner peripheries 32 c of the support rings 32 havethe arcuate convex cross sections. Thus, the contacting ellipsestherebetween approach points as shown by the broken line in FIG. 16(C),with a reduction in area at the same time. As a result, the forces totilt the roller assemblies A decrease greatly as compared to theconventional ones, whereby the rollers 34 further improve in orientationstability.

[0181] Furthermore, in this embodiment, tilt suppressing means asmagnified in FIG. 22 are provided. More specifically, the outerperiphery 34 a of a roller 34 and a roller guideway 14 are brought intoangular contact at two points p and q. The contact angle α₁ at theangular contact point q on the trunnion-bottom side is made greater thanthe contact angle α₀ at the angular contact point p on thetrunnion-extremity side (α₁>α₀). According to this configuration, sincethe outer peripheries 34 a of the rollers 34 and the roller guideways 14are in angular contact with each other at pairs of points p and q, theroller assemblies A are stabilized in orientation with respect to theroller guideways 14. In addition, since the contact angle α₁ is greaterthan the contact angle α₀, the inward components f can be exerted higherat the angular contact points q on the trunnion-bottom sides.Accordingly, the tilts of the roller assemblies A within the plane ofthe diagram (within the cross section perpendicular to the joint axis)are suppressed to ensure smooth rolling of the rollers 34.

[0182] FIGS. 23-25 show under magnification the tilt suppressing meansof tripod type constant velocity universal joints according to sixth toeighth embodiments. Incidentally, the other configurations of the tripodtype constant velocity universal joints according to the sixth to eighthembodiments are identical to those of the tripod type constant velocityuniversal joint according to the fifth embodiment. Thus, descriptionthereof will be omitted.

[0183] The tilt suppressing means according to the sixth embodimentshown in FIG. 23 are the establishment of coincidence between a centerline L2 passing through the center of curvature of the outer periphery34 a of a roller 34 and a center line L1 passing through the center ofcurvature of the inner periphery 32 c of a support ring 32 when thesupport ring 32 makes a relative shift to the trunnion-bottom side withrespect to the roller 34 due to clearances between parts that constitutethe roller assembly A, or in this example, the axial clearances betweenthe support ring 32 and the lock rings 33 and 35. This configuration canbe realized, for example, by shifting the center line L1 of the supportring 32 Δh off the axial center (the axial center of the support ring32) toward the trunnion bottom. This configuration reduces the inwardcomponent f. As a result, the tilts of the roller assembly A within theplane of the diagram (within the cross section perpendicular to thejoint axis) are suppressed to ensure smooth rolling of the roller 34.

[0184] The tilt suppressing means according to the seventh embodimentshown in FIG. 24 are the outer periphery 34 a of a roller 34, shapedinto an arcuate convex section of R in radius, with the center ofcurvature O1 in the vicinity of a line L3 that is parallel to the axisof the roller 34 and passes through the contact portion S. In thisconfiguration, the contact portion S. or the point of application of theinward component f, and the center of curvature O1 of the outerperiphery 34 a of the roller 34, or the fulcrum of the tilts of theroller assembly A, are brought near to each other in the radialdirection of the roller assembly A (clearance Δt). This reduces thetilting moment acting on the roller assembly A. Accordingly, the tiltsof the roller assembly A within the plane of the diagram (within thecross section perpendicular to the joint axis) are suppressed to ensuresmooth rolling of the roller 34. In this connection, the center ofcurvature O1 of the outer periphery 34 a of the roller 34 may be set onthe line L3 (Δt=0).

[0185] The tilt suppressing means according to the eighth embodimentshown in FIG. 25 are the outer periphery 22 a of a trunnion 22, inclinedso as to spread out toward the bottom side in a longitudinal section. Inthe example shown in the diagram, the inclination of the outer periphery22 a is set at such an angle that the outer periphery 22 a becomesparallel to the axis Y of the roller assembly A when the axis X of thetrunnion 22 tilts by an angle β with respect to the axis Y of the rollerassembly A in the above-described manner. That is, the inclination isset at the same angle (β) as the tilt angle β of the trunnion 22. Thisconfiguration eliminates the difference between the direction of theapplied load F and the direction of the torque transfer, therebyprecluding the production of the inward component f. As a result, thetilts of the roller assembly A within the plane of the diagram (withinthe cross section perpendicular to the joint axis) are suppressed toensure smooth rolling of the roller 34. In this connection, even whenthe inclination of the outer periphery 22 a is set below β, a certaineffect can be expected in reducing the inward component f and therebysuppressing the tilts of the roller assembly A.

[0186] While the tripod type constant velocity universal jointsaccording to the fifth through eighth embodiments described above haveemployed the respective tilt suppressing means (FIGS. 22-25) bythemselves, two or more types of tilt suppressing means may be used incombination.

[0187] FIGS. 18(A) through 19 show a tripod type constant velocityuniversal joint according to a ninth embodiment of the presentinvention. The constant velocity universal joint of this embodimentdiffers from those of the above-described embodiments in that thegenerator to the inner peripheries 32 c of the support rings 32, whichhas been a single arc, consists of a combination of an arc portion 32 aat the center and relief portions 32 b on both sides. The role of therelief portions 32 b is to avoid the interference with the trunnions 22at an operating angle (θ) as shown in FIG. 18(C). Each relief portion 32b is formed by a straight or curved line that gradually spreads out froman edge of the arc portion 32 a to an end of the support ring 32. Therelief portions 32 b illustrated here are formed by part of a conicalsurface having a vertex angle α=50°. The arc portions 32 a have a largeradius of curvature (r) on the order of e.g. 30 mm, so as to allow thetrunnions 20 to tilt 2-3° or so with respect to the support rings 32. Intripod type constant velocity universal joints, one rotation of theouter joint member 10 constitutionally produces three nutations of thetripod member 20 about the center of the outer joint member 10. Here,the amount of eccentricity represented by the symbol e {FIG. 17(A)}increases in proportion to the operating angle (θ). While the threetrunnions 22 are spaced by 120° from one another, the presenceof theoperating angle (θ) causes the trunnions 22 to tilt as shown in FIG.17(B). More specifically, with reference to the vertical trunnion 22shown to the upper in the diagram, the remaining two trunnions 22 aredeclined slightly from their axes at the zero operating angle, shown bythe dot-dash lines. For example, an operating angle (θ) of approximately23° causes a decline of the order of 2-3°. This decline can be readilyallowed by the curvature of the arc portions 32 a on the innerperipheries 32 c of the support rings 32. Therefore, the surfacepressures at the contact portions between the trunnions 22 and thesupport rings 32 can be prevented from becoming excessively high.Incidentally, FIG. 17(B) is a schematic representation of the threetrunnions 22 of the tripod member 20 as seen from the left side of FIG.17(A), the full lines showing the individual trunnions. The constantvelocity universal joint of this embodiment also uses tilt suppressingmeans identical to one of those configurations shown in FIGS. 22-25, ortwo or more of them in combination, so that the tilts of the rollerassemblies A within the cross section perpendicular to the joint axisare suppressed to ensure smooth rolling of the rollers 34. Incidentally,the structure shown in FIG. 21 may be adopted for the locking means inthe roller assemblies A.

[0188] While there has been described what are at present considered tobe preferred embodiments of the invention, it will be understood thatvarious modifications may be made thereto, and it is intended that theappended claims cover all such modifications as fall within the truespirit and scope of the invention. TABLE 1 T_(PCD)/S_(PCD) 1.6 1.7 2.12.2 DURABILITY Δ ◯ ◯ ◯ TEST RESULT NEED OF NO NO NO NEEDED INCREASE INOUTER DIAMETER

[0189] TABLE 2 D_(R)/S_(PCD) 1.3 1.48 2.05 2.21 2.33 DURABILITY Δ ◯ ◯ ◯◯ TEST RESULT CRACKS IN NONE NONE NONE NONE FOUND THINNER PORTIONS OFOUTER JOINT MEMBER

What is claimed is:
 1. A constant velocity universal joint comprising:an outer joint member having three track grooves formed in an innerperiphery thereof, each of said track grooves having axial rollerguideways on both sides thereof; a tripod member having threeradially-projecting trunnions; and rollers respectively arranged on saidtrunnions of said tripod member, said rollers being guided by saidroller guideways, wherein at least either induced thrust or slideresistance is regulated within a specification.
 2. The constant velocityuniversal joint according to claim 1 , wherein the tertiary rotationalcomponent of said induced thrust is regulated to or below 30 N (RMS)under the following condition (X1): the number of revolutions R=100-500(rpm), an operating angle θ=0-14 (deg), and load torque T=0.1×Ts (N·m),where “RMS” represents a root means square, and Ts is the minimum statictorsion torque at which a shaft to be coupled to said tripod membercauses a torsion fracture.
 3. The constant velocity universal jointaccording to claim 1 , wherein the tertiary rotational component of saidinduced thrust is regulated to or below 55 N (RMS) under the followingcondition (X2): the number of revolutions R=100-500 (rpm), an operatingangle θ=0-14 (deg), and load torque T=0.2×Ts (N·m), where “RMS”represents a root means square, and Ts is the minimum static torsiontorque at which a shaft to be coupled to said tripod member causes atorsion fracture.
 4. The constant velocity universal joint according toclaim 1 , wherein the tertiary rotational component of said inducedthrust is regulated to or below 80 N (RMS) under the following condition(X3): the number of revolutions R=100-500 (rpm), an operating angleθ=0-14 (deg), and load torque T=0.3×Ts (N·m), where “RMS” represents aroot means square, and Ts is the minimum static torsion torque at whicha shaft to be coupled to said tripod member causes a torsion fracture.5. The constant velocity universal joint according to any one of claims1-4, wherein said slide resistance is regulated to or below 40 N (peakto peak) under the following condition (Y1): the number of revolutionsR=0 (rpm), an operating angle θ=0-10 (deg), load torque T=98-196 (N·m),a vibrating frequency f=15-40 (Hz), and vibrating amplitude=±0.01 to±0.03 (mm), where “peak to peak” represents the total of the absolutevalues of positive and negative peak values.
 6. The constant velocityuniversal joint according to any one of claims 1-4, wherein said slideresistance is regulated to or below 60 N (peak to peak) under thefollowing condition (Y2): the number of revolutions R=0 (rpm), anoperating angle θ=0-10 (deg), load torque T=98-196 (N·m), a vibratingfrequency f=15-40 (Hz), and vibrating amplitude=±0.05 to γ0.08 (mm),where “peak to peak” represents the total of the absolute values ofpositive and negative peak values.
 7. The constant velocity universaljoint according to any one of claims 1-4, wherein said slide resistanceis regulated to or below 80 N (peak to peak) under the followingcondition (Y3): the number of revolutions R=0 (rpm), an operating angleθ=0-10 (deg), load torque T=98-196 (N·m), a vibrating frequency f=15-40(Hz), and vibrating amplitude=±0.10 to ±0.25 (mm), where “peak to peak”represents the total of the absolute values of positive and negativepeak values.
 8. The constant velocity universal joint according to claim1 , comprising roller assemblies for allowing tilting movements of saidrollers with respect to said trunnions.
 9. The constant velocityuniversal joint according to claim 8 , wherein: said roller assembliesinclude said rollers and support rings for supporting said rollersrotatably, said support rings being fitted onto the outer peripheries ofsaid trunnions; the inner peripheries of said support rings have anarcuate convex section; and the outer peripheries of said trunnions arestraight in a longitudinal section, and so shaped in a cross section asto make contact with the inner peripheries of said support rings indirections perpendicular to the axis of the joint and create clearanceswith the inner peripheries of said support rings in the axial directionof the joint.
 10. The constant velocity universal joint according toclaim 9 , wherein said trunnions have a cross section of generallyelliptic shape with the major axis perpendicular to the axis of thejoint.
 11. The constant velocity universal joint according to claim 8 ,wherein: said roller assemblies include said rollers and support ringsfor supporting said rollers rotatably, said support rings being fittedonto the outer peripheries of said trunnions; the outer peripheries ofsaid trunnions have a convex spherical shape; and the inner peripheriesof said support rings have a cylindrical or conical shape.
 12. Theconstant velocity universal joint according to claim 9 , wherein aplurality of rolling elements are interposed between said support ringsand said rollers.
 13. The constant velocity universal joint according toclaim 12 , wherein said rolling elements are needle rollers.
 14. Aconstant velocity universal joint comprising: an outer joint memberhaving three track grooves each having circumferentially-opposed rollerguideways; a tripod member having three radially-projecting trunnions;rollers inserted into said track grooves; and rings fitted onto saidtrunnions, for supporting said rollers rotatably, said rollers beingcapable of moving along said roller guideways in the axial direction ofsaid outer joint member, wherein the ratio of the pitch circle diameterT_(PCD) of said track grooves to the pitch circle diameter S_(PCD) of aspline hole formed in said tripod member, or T_(PCD)/S_(PCD), is setwithin the range of 1.7-2.1, the ratio of the diameter D_(J) of saidtrunnions to the pitch circle diameter S_(PCD) of said spline hole, orD_(J)/S_(PCD), is set within the range of 0.6-1.0, and the ratio of theouter diameter D_(R) of said rollers to the pitch circle diameterS_(PCD) of said spline hole, or D_(R)/S_(PCD), is set within the rangeof 1.4-2.3.
 15. The constant velocity universal joint according to claim14 , wherein: said rings have a spherical cross section; said trunnionsare so shaped in a cross section as to make contact with the innerperipheries of said rings in directions perpendicular to the axis of thejoint and create clearances with the inner peripheries of said rings inthe axial direction of the joint; the ratio T_(PCD)/S_(PCD) is setwithin the range of 1.72-2.10; the ratio of the dimension D_(JL) of saidtrunnions in the directions perpendicular to the axis of the joint tothe pitch circle diameter S_(PCD) of said spline hole, orD_(JL)/S_(PCD), is set within the range of 0.63-0.94; and the ratioD_(R)/S_(PCD) is set within the range of 1.47-2.21.
 16. The constantvelocity universal joint according to claim 14 , wherein the ratio ofthe outer diameter D_(O) of said outer joint member to the pitch circlediameter S_(PCD) of said spline hole, or D_(O)/S_(PCD), is set withinthe range of 2.78-3.77.
 17. The constant velocity universal jointaccording to claim 14 , wherein the ratio of the barrel width H_(T) ofsaid tripod member to the pitch circle diameter S_(PCD) of said splinehole, or H_(T)/S_(PCD), is set within the range of 0.81-1.22.
 18. Theconstant velocity universal joint according to claim 14 , wherein theratio of the width H_(R) of said rollers to the pitch circle diameterS_(PCD) of said spline hole, or H_(R)/S_(PCD), is set within the rangeof 0.38-0.67.
 19. The constant velocity universal joint according toclaim 14 , wherein the ratio of the radius of curvature R_(R) of theouter peripheries of said rollers to the pitch circle diameter S_(PCD)of said spline hole, or R_(R)/S_(PCD), is set within the range of0.19-1.11.
 20. A constant velocity universal joint comprising: an outerjoint member having three axial track grooves formed in an innerperiphery thereof, each of said track grooves having axial rollerguideways on both sides thereof; a tripod member having threeradially-projecting trunnions; and roller assemblies respectivelymounted on said trunnions of said tripod member, said roller assembliesincluding rollers to be guided along said roller guideways in directionsparallel to the axis of said outer joint member and support rings forsupporting said rollers rotatably, said roller assemblies being capableof tilting movements with respect to said trunnions, the constantvelocity universal joint further comprising tilt suppressing means forsuppressing tilts of said roller assemblies within a cross sectionperpendicular to the axis of the joint due to inward components of loadapplied to contact portions between said trunnions and said rollerassemblies.
 21. The constant velocity universal joint according to claim20 , wherein said tilt suppression means are effected by establishingtwo-point angular contact between the outer peripheries of said rollersand said roller guideways, and making the contact angle at angularcontact points on the trunnion-bottom sides greater than the contactangle at angular contact points on the trunnion-extremity sides.
 22. Thecontact velocity universal joint according to claim 20 , wherein saidtilt suppressing means comprise the outer peripheries of said rollers,shaped into arcuate convex sections having the centers of curvature inthe vicinities of lines parallel to the axes of said rollers, said linespassing through said contact portions.
 23. The constant velocityuniversal joint according to claim 20 , wherein: the inner peripheriesof said support rings have an arcuate convex section; the outerperipheries of said trunnions are straight in a longitudinal section,and so shaped in a cross section as to make contact with the innerperipheries of said support rings in direction perpendicular to the axisof the joint and create clearances with the inner peripheries of saidsupport rings in the axial direction of the joint.
 24. The constantvelocity universal joint according to claim 23 , wherein said trunnionshave a cross section of generally elliptic shape with the major axisperpendicular to the axis of the joint.
 25. The constant velocityuniversal joint according to claim 23 , wherein said tilt suppressingmeans are effected by establishing coincidence between center linespassing through the respective centers of curvature of the outerperipheries of said rollers and center lines passing through therespective centers of curvature of the inner peripheries of said supportrings when said support rings make relative shifts with respect to saidrollers due to clearances between parts constituting said rollerassemblies.
 26. The constant velocity universal joint according to claim23 , wherein said tilt suppressing means comprise the outer peripheriesof said trunnions, inclined so as to spread out toward the trunnionbottoms in their longitudinal sections.
 27. The constant velocityuniversal joint according to claim 20 , wherein a plurality of rollingelements are interposed between said rollers and said support rings.